A car travels from city A to city B at an average speed of 60 km/h and returns at an average speed of 40 km/h. What is the average speed for the entire trip?
Correct: A
To find the average speed for the entire trip, we use the formula: Average Speed = Total Distance / Total Time. Since the distance from A to B is the same as from B to A, let's denote this distance as D. The time taken to travel from A to B is D/60 and the time taken to travel back is D/40. The total time is D/60 + D/40. Finding a common denominator, we get (2D + 3D)/120 = 5D/120 = D/24. The total distance is 2D. So, the average speed = 2D / (D/24) = 2 * 24 = 48 km/h.